It is known to provide an automatic slack adjuster for operably connecting a brake operator to a cam shaft forming part of a vehicle brake system of the type including a housing; a worm gear mounted by the housing for rotation with the cam shaft about a first axis; a worm shaft mounted by the housing to rotate about a second axis perpendicular to the first axis and for displacement axially of the second axis, wherein the worm shaft has opposite ends and a worm arranged intermediate such ends for engagement with the worm gear; a rotor and a coupling each mounted coaxially to rotate relative to one end of the worm shaft; a clevis for connecting the housing to the brake operator for rotating the housing in opposite directions about the first axis as the vehicle brakes are applied and released; a link for connecting the clevis to the rotor for rotating the rotor in opposite directions about the second axis as the vehicle brakes are applied and released; a one way clutch tending to couple the coupling for rotation with the rotor when the rotor is rotated in one direction and tending to uncouple the coupling from rotation with the rotor when the rotor is rotated in an opposite direction; a slip device for releasably connecting the worm shaft for rotation with the coupling; and a spring tending to bias the worm shaft axially to rotatably connect the worm shaft to the coupling via the slip device, while permitting oppositely directed axial movement of the worm shaft to rotationally disconnect the worm shaft from the coupling upon a given axial loading of the worm shaft by the cam shaft.
Slack adjusters of the type generally described above are of two general types, namely, a first type wherein slack adjustments are effected during brake application, as disclosed for example in U.S. Pat. No. 4,380,276, and a second type wherein slack adjusters are effected during brake release, as disclosed for example in U.S. Pat. No. 3,351,163.